Field of the Invention
The invention lies in the automotive art. More particularly, the invention relates to a method of locating an enabling component containing a transponder for a vehicle and to a motor vehicle with a device for locating an enabling component containing a transponder.
Keyless entry systems for motor vehicles are gaining in significance. This is not only for reasons of convenience, but they also increase security against theft. Keyless entry systems include an enabling component which replaces the previously conventional car key. The enabling component contains a transponder which, upon receiving a request signal transmitted by a transmitter in the vehicle, transmits an encoded signal with vehicle-specific and/or user-specific information. Upon receiving the encoded signal by the vehicle-side receiver, the signal is evaluated and the vehicle is enabled for operation.
German published non-prosecuted patent application DE 41 23 654 A1 discloses a system with two antennas disposed in the rear-view mirrors and with associated transmitting/receiving units. The system locates and determines whether the enabling component is located outside the vehicle when a request to lock the vehicle is received. The system thus ensures that the vehicle is locked when the enabling component is located inside the vehicle.
One problem that occurs in the context of keyless entry systems is that the driver, or another person holding the enabling component, loses the reference to the current location of the enabling component. The enabling component, which may be a "smart card", specifically only has to be brought somewhere into the starting enabling region of the vehicle in order that the vehicle can be put into operation without a key or the like, merely via the operating elements on the dashboard. If the driver subsequently wishes to leave the vehicle, she must first search for the enabling component. This may be quite tedious and, if any, there is usually very little time for such a search.
German published non-prosecuted patent application DE 42 40 426 A1 discloses a motor vehicle with an electronic access control system that operates with a dialog between the vehicle and an enabling component carried by an individual. The enabling component contains a transponder. In order that the enabling component does not inadvertently remain in the vehicle, for example when the door is closed with the central lock actuated, a dialog commences between at least one transmitter/receiver in the vehicle and the enabling component after the door has been closed. A search signal transmitted by the transmitter/receiver is received by the enabling component only if it is located inside the vehicle. The enabling component then sends a response signal from which a logic system connected downstream of the transmitter/receiver concludes that the enabling component is located in the vehicle, and unlocks the central locking for a predetermined time period and generates an acoustic warning signal. The exact location at which the enabling component is to be located is not described in the publication.